The present invention relates to dry-cleaning systems and, more particularly, to a liquified gas dry-cleaning system having a cleaning vessel with improved means for agitating contained items for enhanced and more efficient cleaning.
Known dry-cleaning processes consist of a wash, rinse, and draining/drying cycle with solvent recovery. During the dry-cleaning process, items, such as garments, are loaded into a basket disposed within a vessel and immersed in a dry-cleaning solvent that is pumped into the vessel from a base tank. Conventional dry-cleaning solvents include perchloroethylene (PCE), petroleum-based or Stoddard solvents, CFC-113, and 1,1,1-trichloroethane, all of which are generally aided by a detergent.
The use of these conventional solvents, however, poses a number of health and safety risks as well as being environmentally hazardous. For example, halogenated solvents are known to be environmentally unfriendly, and at least one of these solvents, PCE, is a suspected carcinogen. Known petroleum-based solvents are flammable and can contribute to the production of smog. Accordingly, dry-cleaning systems which utilize dense phase fluids, such as liquid carbon dioxide, as a cleaning medium have been developed. An apparatus and method for employing liquid carbon dioxide as the dry-cleaning solvent is disclosed in U.S. Pat. No. 5,467,492, entitled xe2x80x9cDry-Cleaning Garments Using Liquid Carbon Dioxide Under Agitation As Cleaning Mediumxe2x80x9d. A similar dry-cleaning apparatus is also disclosed in U.S. Pat. No. 5,651,276.
These systems pose a number of other problems, particularly in relation to the high operating pressures necessary for maintaining the gas in a liquid state. Specifically, the cleaning vessel in a liquid carbon dioxide dry-cleaning system operates at between 700-850 psi under ambient temperature conditions. The dry-cleaning solvent functions to dissolve the soluble soils on the item. The insoluble soils, however, must be physically dislodged from the item, which typically required agitation of the items in the cleaning solvent during the wash and rinse cycles.
In dry-cleaning systems that utilize liquified gas as a cleaning solvent, it has been particularly difficult to effect agitation sufficient to clean items of extremely fine unsoluble soils, such as dirt or like particles three microns and less in size. Because of the high operating pressures under which the liquified gas must be maintained, care also must be taken to prevent damage to the goods from pressurized streams of liquified gas introduced into the cleaning vessel.
Furthermore, in liquified gas dry-cleaning systems it is necessary that the liquified gas be completely removed from the cleaned items, vaporized to separate the contaminants and foreign particulate matter, and reliquified for re-circulation through the system. The cycle time for such processing can be lengthy, thereby increasing the operating cost. The presence of air in the liquid carbon dioxide cleaning solvent, such as air that enters the cleaning solvent from items introduced into the system for cleaning, also can adversely affect the cleaning process. Heretofore methods of removing or venting such air have not been effective.
Accordingly, a need exists for an improved dry-cleaning system, and in particular, an improved liquified gas dry-cleaning system.
It is an object of the present invention to provide an improved liquified gas dry-cleaning system which enables faster cleaning and quicker solvent removal upon completion of the cleaning cycle.
Another object of the invention is to provide a liquified gas dry-cleaning system as characterized above that has an agitation system adapted for enhanced cleaning and shortened cycling times.
Still another object is to provide a liquified gas dry-cleaning system of the above kind that effects thorough agitation of items during the cleaning cycle without damage to relatively fragile garments and the like.
Yet another object is to provide a liquified gas dry-cleaning system of the foregoing type that is more effective for preventing contamination of the liquified gas cleaning solvent with air. A related object is to provide such a dry-cleaning system that is operable for more effectively removing air from the system prior to introduction of the liquified gas into the cleaning chamber.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: